In most cases it seems as though when the port in the manifold is larger than the head, there is no loss in HP. The other way around is not good. I believe it's a situation where the edge stops reversion pulses. Extrude honing is done by machine. They force a cutting medium through the port under pressure. It removes objects in it's way, so the most restrictive areas get opened up first.

Frank/Rebop

Bristol, In ( by Elkhart) 

Thank you for the advice will give it a shot!

Put some double sided tape (the spongy kind) on the manifold flange. Mount the manifold and tap it with a hammer. There will be an imprint in the tape. Cut along the imprint with a razor blade and transfer the line to the manifold or head, which ever you are working on. Put a little grease on the side of the tape you want to release. You can use this approach for making brackets that will mount to blind holes or for making gaskets etc. when a transfer punch won't work. Have fun.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia

Here’s the link to the site mentioned above.

.

http://boneheadperformance.com/extrude-honing/

Lorena, Texas (South of Waco)

Hi Jeff,

I have not had experience with extrude honing, but some Forum members have previously spoken of having utilizing it. -I believe that the use cited in threads here has pertained to intake manifolds...

For an informative tutorial on the use of this industrial process for engine modification purposes, Google boneheadperformance.com When the web page opens, toggle their subheading, 'Extrude Honing'. This company specializes in engine 'extrude hone porting' along with powder coating and ceramic coating work.
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Related issue...

My understanding is that MATCHING exhaust manifold flange openings to cylinder head exhaust ports is NOT something that is desirable to do. Making the exhaust manifold flange openings LARGER than the cylinder head exhaust port openings will leave an edge that will serve to reduce exhaust back flow which I've read is desirable...

I am no expert on exhaust header design. There are other Forum members who can more knowledgeably contribute on this subject, I'm sure.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Hey Guys,

Thanks for the input.....But I, don't know what extrude honing is? since the engine is in the car I was going to remove the manifolds and with a carbide cutter on a die grinder remove some material. I, understand the reasoning behind match poring.....But how would I, do this? I was wondering if there would be an out line of carbon around the ports to indicate an outline on where to grind? Also I'm guessing I, should remove the heat riser valve on the Pass. side and put in a blank spacer?

Thank you for the input and the help. I, feel better about attempting this now that I've asked for advice..

Jeff

"extrude honing"...??

"God Bless Texas"location: Houston,TX

Paul. I'd say yes to extrude honing on the exhaust manifolds. It seems to work quite well for the muscle car guys that must run factory manifolds in those classes that require stock appearing engines right down to the cast iron exhaust manifolds.

Lorena, Texas (South of Waco)

Ted,

Would extrude honing be a good thing to do on the stock exhaust manifolds? Header choices are limited and the stock manifolds seem to be equal or a little better than what are reasonably available for passenger cars.

Paul J. - '57 E Code

There should be enough material on the manifold flanges to match port them to your heads. The more the engine is built up (heads, camming, compression, etc.), the more that gain will be seen from doing any exhaust manifold porting. Any restriction at the exhaust is obviously going to be a detriment from a performance standpoint but exactly how much is going to be difficult to determine without some kind of definitive testing. I'm thinking the difference gained will be the same as found in going form the '56 to '57 exhaust manifolds if I was to take a random guess.

Lorena, Texas (South of Waco)